JPH06652B2 - Method for producing piezoelectric ceramic powder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a piezoelectric ceramic powder made of lead zirconate titanate tin antimonate for use in filters, spark plugs and the like.

Conventional structure and its problems Conventional piezoelectric ceramic powders of lead tin antimonate titanate zirconate have the following 1st PbO, TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O as shown in the flow chart. Various oxide powders of ₃ are blended according to the intended composition, mixed in a wet ball mill, dried in 2, calcined in 3 to cause solid phase reaction, pulverized in 4 in a wet ball mill and dried in 5. To manufacture. The drawbacks of this method are that the degree of homogeneity of the composition is poor from the microscopic point of view, and the powder diameter is also relatively large and it is difficult to reduce the particle diameter to 1 μm or less. Therefore, when the sintered body was processed into a thin plate, the strength of the thin plate was insufficient.

However, when used as a filter, when the resonance frequency is in the MHz band, vertical thickness vibration and thickness shear vibration are used. In this case, the resonance frequency is determined by the material constant and the thickness of the element, and the higher the resonance frequency, the thinner the element is required to be. For example, the frequency constant is 950Hz ・ m
With the above material, the element thickness is about 210 μm to obtain a resonance frequency of 4.5 MHz.

Therefore, there is a demand for a homogeneous and fine-grained piezoelectric ceramic powder. The coprecipitation method and the alkoxide method are known as homogeneous methods for producing fine particles. PZT or PLZT in the coprecipitation method
Although the synthesis of is already known in the literature, etc., the more components, the more difficult the synthesis becomes. Further, in the alkoxide method, since the metal alkoxide of each component has to be synthesized once, the manufacturing method is complicated and not practical.

OBJECT OF THE INVENTION It is an object of the present invention to provide a method for producing a piezoelectric ceramics powder made of lead tin antimonate titanate titanate zirconate, which is homogeneous and has a small particle size, by a coprecipitation method.

In order to achieve the above-mentioned object, the present invention uses Pb, Ti, Zr, Sn from a mixed nitric acid aqueous solution of lead acetate, titanium oxynitrate, zirconium oxynitrate, and stannous acetate using an aqueous ammonia solution as a precipitant. In the process of co-precipitating the complex consisting of the respective elements, the antimony oxide is added and mixed to form a precipitate, which is then washed, dried and dried.
A method for producing a piezoelectric ceramic powder, which comprises calcination at 0 ° C to 800 ° C. Here, titanium oxynitrate is produced by adding an aqueous nitric acid solution to titanium tetrapropoxide or titanium tetrabutoxide, or titanium tetrachloride is made into titanium hydroxide with aqueous ammonia and then added with an aqueous nitric acid solution.

Description of Embodiments An embodiment of the present invention will be described below with reference to the flowchart of FIG.

The starting material is weighed so as to have a desired composition and subjected to the following treatment. 6 lead acetate _{Pb (CH 3 COO) 2 ·} 3H 2 O and zirconium oxynitrate _{ZrO (NO 3) 2 · 2H} 2 O were dissolved in pure water, titanium tetrapropoxide Ti (OC ₃ H _{7) 4} to 5 times It is mixed with a nitric acid aqueous solution diluted to 1 to prepare a titanium oxynitrate TiO (NO ₃ ) ₂ solution, and stannous acetate is dissolved in a 5 times diluted nitric acid aqueous solution. These are added to a nitric acid aqueous solution and stirred to obtain a mixed nitric acid aqueous solution for coprecipitation. The pH of this aqueous solution is about 1. Also, in step 7, antimony oxide Sb ₂ O ₃ is weighed out in a desired composition. Using a mixer, add diluted ammonia water 8 to the reaction tank, and while stirring vigorously, add antimony oxide powder, and at 9, add the mixed nitric acid aqueous solution for coprecipitation and the ammonia aqueous solution of the precipitating agent to the liquid in the reaction tank. Add pH while adjusting so that it is in the range of 7-8. The precipitate obtained by this operation is washed with 10 times, and then dispersed in pure water.
Spray dried at 1. This powder was calcined at 12 at 600 ° C. for 2 hours, pulverized at 13 by a wet ball mill and dried at 14, to prepare a piezoelectric ceramic powder made of lead tin antimonate titanate zirconate. The particles of the precipitate obtained by this method are extremely fine on the order of 100 Å except for the antimony oxide added as a powder. Therefore, it was confirmed by X-ray analysis that the reactivity was good and that the perovskite had a single-phase crystal structure at a calcination temperature near 550 ° C. In the conventional method, the calcination temperature at which the perovskite has a single-phase crystal structure was about 850 ° C. The average particle size of the powder is 0.8 μm, which is smaller than the average particle size of 1.6 μm in the conventional method.

Next, according to the method of the present invention and the conventional method, powders of lead zirconate titanate antimonate titanate having different compositions were prepared, and a thin plate sliced to a thickness of 200 μm from these sintered bodies was prepared. Were compared. The results are shown in the table below. When the powder according to the method of the present invention is used, the bending strength of the sintered body is improved.

In the method of the present invention, antimony is added as an oxide powder, but since the melting point of antimony oxide is as low as 656 ° C,
Oxide was added because it was easy to react even at a relatively low temperature of calcination.

In this example, titanium oxynitrate TiO (NO ₃ ) ₂ was made from titanium tetrapropoxide, but it was made by adding an aqueous nitric acid solution to titanium tetrabutoxide, or titanium tetrachloride was made into titanium hydroxide with aqueous ammonia, and this Similar results can be obtained by adding an aqueous nitric acid solution. If the calcination temperature is lower than 550 ° C, the reaction due to calcination is not sufficient, and if it is higher than 800 ° C, the particle size grows large, the reactivity decreases, and fine particles are produced by the coprecipitation method. Will not fit in.

Effects of the Invention As described above, the powder of lead tin antimonate titanate zirconate powder produced by the method of the present invention is fine particles, and the sintered body obtained from this has a bending strength higher than that of the conventional method. It is strong and effective for use as a thin plate such as a high frequency filter.

[Brief description of drawings]

FIG. 1 is a flow chart showing a conventional process for producing piezoelectric ceramic powder, and FIG. 2 is a flow chart showing a process for producing piezoelectric ceramic powder according to an embodiment of the present invention.

Claims (2)

[Claims] 1. From a mixed nitric acid aqueous solution of lead acetate, titanium oxynitrate, zirconium oxynitrate, and stannous acetate,
Using an aqueous ammonia solution as a precipitant, Pb, Ti, Zr,
In the process of co-precipitating a complex consisting of Sn elements, antimony oxide is added and mixed to form a precipitate, which is then washed, dried, and calcined at 550 ° C to 800 ° C. A method for producing a piezoelectric ceramic powder, comprising: 2. Titanium oxynitrate is produced by adding an aqueous nitric acid solution to titanium tetrapropoxide or titanium tetrabutoxide, or titanium tetrachloride is made into titanium hydroxide with aqueous ammonia and then added with an aqueous nitric acid solution. The method for producing a piezoelectric ceramic powder according to claim (1).